Palladium compositions suitable as oxidation catalysts

ABSTRACT

1. AN AQUEOUS HOMOGENEOUS SOLUTION CONSISTING ESSENTIALLY OF (A) A WATER-SOLULBE PALLADIUM (II) SALT, SAID SALT BEING SELECTED FROM THE GROUP CONSISTING OF A CHLORIDE, BROMIDDE, NITRATE, SULFATE, AND LI2PDCL4, HAVING A CONCENTRATION OF METAL ION OF AT LEAST ABOUT 0.00005 TO ABOUT 0.025 MOLE PER LITER, (B) COPPER (ii) CHLORIDE OR BROMIDE, (C) A COPPER (II) SALT SELECTED FROM THE GROUP CONSISTING OF A NITRATE, SULFATE, ALKYLSULFONATE, ARYLSUFONATE, TETRAFLUOROBORATE, PERCHLORATE, TRIFLUOROACETATE, TRICHLOROACETATE AND METHANEPHOSPHONATE, AND (D) THE BALANCE WATER, WHEREIN THE TOTAL CONCENTRATION OF (B) AND (C) IS FROM ABOUT 0.003 TO ABOUT 3 MOLES PER LITER, AND WHEREIN THE COPPER (II) CHLORIDE OR BROMIDE (B) COMPRISES FROM ABOUT 10 TO ABOUT 80 MOLE PERCENT OF THE TOTAL OF (B) AND (C).

Nov. 19,1974 c w. G. LLOYD ETAL 3,849,336

PALLADIUI COMPOSITIONS SUITABLE AS OXIDATION CATALYSTS Original FiledFeb. 7. 1972 Effect of Copper(li) Chloride Copperfll) Nitrate Rotio UponEfficiency of Catalyst Solutions lOO 8O 6O 4O 20 O l l I l l I l I 2Percent Copper (H)Nitr0te of Total CopperSoits 0004 M Pact 0.001 M PdC|Percent Conversion of Carbon Monoxide t0C0rb0n Dioxide i l I Q l 0 O 2O4O 6O 80 I00 Percent Copper (It) Ch|0ride of Total Copper Salts (TotolCopper Solt Concentration I.OO Moles per Li t er) nited States PatentOffice 3,849,335 Patented Nov. I9, 1974 US. Cl. 252433 Claims ABSTRACTOF THE DISCLOSURE Homogeneous and heterogeneous catalysts systemscontaining certain palladium (II) salts and copper (II) salts have beendeveloped. A specified balance of a copper (II) halide and of anon-halide copper (II) salt is maintained. The catalysts are effectivefor oxidizing CO to CO and S0 and S0 This is a division, of applicationSer. No. 223,970, filed Feb. 7, 1972, now Pat. No. 3,799,662.

FIELD OF INVENTION This invention has to do with compositions containinga palladium (II) salt, a copper (II) halide and a non-halide copper (II)salt. The compositions are effective oxidation catalysts, particularlyfor the oxidation of CO to CO and S0; to 50 BACKGROUND OF INVENTION Inrecent years, considerable attention has been given to methods forremoving CO and S0 from our environment. CO is a pollutant, particularlyas an exhaust product from motor vehicles. Nationally the transportationindustry is responsible for 42% of the total air contaminants emitted tothe atmosphere; and carbon monoxide, a colorless, odorless and lethalgas, being one of the major components of automobile exhausts is thelargest single air pollutant. Of the 90.5 million tons of carbonmonoxide emitted in 1968 to the atmosphere, 63.8 million tons or 71%came from transportation activities. S0 is also a pollutant, butgenerally as a product from the burning of relatively high sulfurheating oils and coals.

The oxides of sulfur on a national basis in 1968 accounted for anestimated 33 million tons, or -16% of the total emitted aircontamination. Of this, fuel combustion by stationary sources accountedfor 24.4 million tons or 74% of the total oxides of sulfur. The mostimportant air pollutants among the oxides of sulfur are sulfur dioxide,SO and sulfur trioxide, S0 The estimate ratio of S0 to S0 in theatmosphere of Chicago is 100:1. The conversion of S0 to S0 in air isvery slow. The major source of S0 is from the combustion ofsulfur-containing fuels.

Many catalysts and cambinations of catalysts have been proposed toconvert CO to CO and/or SO to S0 or sulfuric acid. These have sufferedfrom a variety of disadvantages, including high cost, highsusceptibility to poisoning and short catalyst lifetimes, low conversionrates at low temperatures or at low flow rates or at low Iconcentrations of the contaminant gas, high head loss, and

undesirable side reaction products. For example, a copper chromitecatalyst in the presence of water vapor converts nitrogen oxides toammonia; an iron oxide-iron sulfate catalyst emits hydrogen sulfide;uranium on alumina is not effective at low CO' concentrations; manganeseoxide is unsuited to high-temperature operation; hopcalite catalysts arepoisoned by water vapor.

Most of the known art of palladium-catalyzed oxidations is directed tothe oxidation of olefins to carbonyl compounds, mainly acetaldehyde andketones. This reaction, as well as the palladium (II) chloride oxidationof CO, was first reported by F. C. Phillips (Z. anorg. Chem., 6, 229(1894)).

Dragerwerk (German 713,791) shows the successful incorporation ofpalladium (II) chloride and copper (II) chloride to obtain the catalyticoxidation of 60 using atmospheric oxygen as the ultimate oxidant. ThusExample 1 uses a dilute hydrochloric acid solution of PdClg and CuCland, like Phillips, recommends elevated temperatures (SO- C.). BothPhillips and Dragerwerk worked with halide salts, and both found itdesirable to operate at somewhat elevated temperatures in order toovercome the sluggishness of the reaction at ambient temperatures. Thishas also been observed in more recent studies by Markov (V. D. Markovand A. B. Fasman, Zh. Fiz. Khim., 40, 1564 (1966); V. D. Markov, V. A.Golodov, and A. B. Fasman, Izv. Sib. Otd. Akad. Nauk SSSR, Ser. Khim.Nauk, 1968, 36), who worked with excess chloride or bromide ions presentand who found the reaction between Pd (II) and Co to be slow as to bethe rate-determining step of the overall reaction.

Lloyd (U.S. 3,410,807) has described the chemistry of homogeneoussolutions of palladium (II) and copper (II) salts in alcoholicsolvent-media. In substantially dry alcoholic systems (less than 2%water), CO is reacted with the alcohol solvent-reactant to synthesizeorganic carbonate esters; similarly, S0 is reacted to synthesize organicsulfate esters. For the purposes of air pollution control and abatement,these reaction systems would release exit gas streams saturated with thevolatile alcoholic solvent-reactant, and would be unacceptable from bothan economic and environmental standpoint, and in the case of COoxidation would require side-stream removal of the carbonate esterformed in the reaction.

The first reported supported catalytic oxidation of CO with Pd (II) andCu (II) appears in the Dragerwerk patent. More recent work withsupported palladium catalysts makes use of zerovalent palladium metaland, typically, copper oxides upon alumina or silica support. It shouldbe noted that, although some of this literature makes use of palladium(II) chloride and copper (II) chloride in catalyst preparation, it isusually explicitly evident and is always implicitly evident from aconsideration of the thermal stabilities and properties of the inorganiccompounds involved, that the actual catalyst involves palladium (O) anda mixture of copper oxides and basic copper choride. For example, Keggi(French 1,539,443) treats an inert support with a solution containingpalladium (II), copper (II), and aluminum (III) chlorides, dries thesupport, then calcines at 600 C' for two hours. At this temperature,well above the decomposition temperature of palladium (II) chloride,PdCl is reduced to Pd (0). This temperature is also well above themelting point of copper (II) chloride and the sublimation temperature ofaluminum (III) chloride. Indeed, as Keggi reports, the totalconcentration of chloride remaining on and in the calcined catalyst isvery low.

The present invention is directed to the provision of new and superioroxidation catalysts, which are particularly effective for the conversionof CO to CO and 50 to S0 SUMMARY OF THE INVENTION In accordance with thepresent invention, there are provided oxidation catalysts comprisingaqueous homogenous solutions containing specified proportions of awatersoluble palladium (II) salt, a copper (II) halide, a copper (II)salt of an oxyanion derived from a strong acid, and the balancesubstantially water. There are also provided heterogeneous oxidationcatalysts comprising specified proportions of the water-solublepalladium (II) salt, the copper (II) halide and the other copper (II)salt, with or without an appropriate carrier.

There are also provided processes for oxidizing CO and S to CO and S0respectively, by contacting a gaseous charge containing CO and/ or S0with a catalyst of the character specified above.

SPECIFIC EMBODIMENTS OF THE INVENTION As indicated above, thecompositions of this invention contain a water-soluble palladium (II)salt. Typical of such salts are the: chloride, bromide, nitrate, sulfateand Li PdCl Particularly preferred is palladium (II) chloride.

The concentration of the palladium (II) salt in the homogeneoussolutions can range from at least about 0.00005 mole per liter to thesolubility of the salt in water. Preferred concentrations range fromabout 0.001 to about 0.02M.

A mixture of copper (II) salts (b) and (c), is employed. One salt (b) isa halide, namely the chloride or bromide. The chloride is preferred. Theother salt (c) is a non-halide, and is a salt of an oxyanion derivedfrom a strong acid. Typical of (c) are: nitrate, sulfate, alkylsulfonate(e.g. methanesulfonate), trifiuorornethanesulfonate, aryl sulfonate(e.g. p-toluenesulfonate, tetrafluoroborate, perchlorate,trifluoroacetate, trichloroacetate and methanephosphonate.

The total concentration of the copper (II) salts (b) and (c) ranges fromabout 0.003 to about 3, and preferably 0.1 to 2.0 moles per liter.Solutions with very low copper (II) concentrations, below 0003M, arelimited in the rate at which reduced palladium (O) can be reoxidized,and in unfavorable operating conditions may precipitate reducedpalladium metal, removing it from the homogeneous system with consequentloss of catalytic activity. At copper (II) salt concentrations aboveabout 3 moles per liter two disadvantageous factors emerge: increasedsolution viscosity which impairs the ease and efficiency of gas-liquidmixing, and the possibility of exceeding salt solubilities andprecipitating catalyst or co-catalyst under actual operating conditionsin which water evaporation may involve fluctuations in Water content.

A critical relationship of the aqueous homogeneous catalysts is thebalance of copper (II) halide (b) and the other copper (II) salt (c). Ithas been found that superior results are realized by employing fromabout to about 80, and preferably -60, mole per cent of salt (b) of thetotal of (b) and (c), with (c) the remainder.

Stated in another manner, the approximate concentration relationships ofthe several components are as follows:

0.005-10, preferably 0.1-2, grams per liter of palladium 10-80,preferably 15-60, mole per cent of copper (II) salt (b) of the totalcopper (II) salts.

The chloride ion concentration is 0.1-0.9 preferably 0.2- 0.7, times theweight of copper (II); or, when bromide ion is present instead ofchloride ion, the bromide ion concentration is 0.25-2, preferably0.4l.5, times the weight of copper (II) present.

As mentioned above, the palladium (II) salt can be in the form of LiPdCl Thus, LiCl in association with PdCl serves to facilitatedissolution of PdCl in water. In this regard, it has been found thatwhen PdCl and LiCl are added to a solution containing copper (II) salts(b) and (c), the resulting solution is effective as an oxidationcatalyst; however, when the resulting solution is allowed to age atambient temperature (25 C.) for 4 about three hours or more, it issubstantially more effective as an oxidation catalyst.

In addition to the palladium (II) salt (a) and the copper (II) salts (b)and (c), the homogeneous solutions can also contain a compatiblechloride or bromide salt to aid in the dissolving of the palladium (II)salt. Chloride and bromide salts of Group IA and Group IIA metals, forexample, have no adverse effect upon the catalytic activity of thesolutions. The solutions can also contain any other dissolved saltswhich are compatible with the palladium (II) and copper (II) salts, thatis, which do not form specific complexes or precipitates of copper (II)or palladium (II). It should be noted that when a salt such as lithiumsalt is included, the halide/non-halide ratio, (b)/ (c), applies to thetotal anion concentrations.

The solutions are prepared by adding the salts (a), (b) and (c), with orwithout a chloride or bromide salt of a Group IA and/or Group IIA metal,to water in the concentrations specified above. Other than the agingeffect already mentioned with respect to a solution containing LiCl, theparticular order of addition of salts (a), (b) and (c) to water has nosubstantial influence upon the catalytic effectiveness of the resultingsolution.

When the homogeneous catalysts are employed for the oxidation of CO toCO and S0 to S0 the temperature used can be from about 0 C. to about C.,and preferably at 1050 C., at atmospheric pressure. Variation inpressure can range from subatmospheric (the limit being the vaporpressure exerted by the catalyst solution) through to superatmospheric,with the preferred pressure being at or near atmospheric pressure.

Flow rates depend upon the geometry of the apparatus employed. Contacttime will range from about 0.1 second to about 5 seconds, with apreferred range of 0.3-3 seconds.

The CO partial pressure can be any fraction of the total gas pressure.CO removal at partial pressures as low as 4 10 atmospheres, which is thelimit of the detection system employed, has been accomplished. For $0any partial pressure which does not liquify it is acceptable. With thepreferred total pressure close to atmospheric, the preferred partialpressures of these reactant gases are 00.5 atmospheres.

If there should be less than a stoichiometric excess of oxygen in thefeed gas (with respect to CO and/or S0 then the catalyst solution shouldbe contacted periodically with an oxygen-containing gas, such as air, inorder to reoxidize copper (I) and retain catalyst activity. This can bedone by continuous recycling or batch treatment.

The heterogenous catalysts of this invention comprise a support materialimpregnated with specified amount of the palladium (II) salt (a) and ofthe copper (II) salts (b) and (c). Here again, the water-solublepalladium (II) salts (a) and copper (II) salts (b) and (c), above, areemployed. Typical supports include alumina, silica, silica alumina,zirconia, thoria, aluminum silicates, zeolites, magnesia, siliconcarbide and the like. Such supports are well known in the art and areavailable commercially. Particularly useful are those supports which canbe used at temperatures generally existing in vehicle exhaust systemsand industrial stacks.

The supported catalysts are repared by contacting an aqueous homogeneoussolution with a suitable support, and slurrying the solution with thesupport at 0 C.300 C., preferably 60150 C., for 5-60 minutes. Thesupport which has become impregnated with the solution is separated fromthe remaining solution, as by suction filtration, and is dried. Dryingcan be accomplished with an aspirator air stream for several minutes,then by keeping the impregnated support under vacuum (e.g. 20 mms.) at2025 C. for 16 hours, followed by about 24 hours at 20 mms. vacuum at 60C. There is no need to calcine the catalyst.

The resulting supported catalysts will contain: at least about 0.00001,preferably 0.0003 to 0.03 gram-moles of palladium (II) salt per kilogramof inert support, and the total copper (II) salts from about 0.001 toabout 1.5, preferably 0.03-0.8, gram-moles per kg, with the sameapproximate ratio of (b)/(c) as specified above.

The concentration relations can also be expressed:

0.001-10, preferably 0.33, grams of palladium (II) per kilogram of inertsupport,

0.06-100, preferably 2-50, grams of copper (II) per kilogram of inertsupport,

-80, preferably 60, mole percent of copper (II) salt (b) of the totalcoper (II) salts.

The chloride and bromide concentrations are the same as those givenabove for homogeneous catalysts.

Here also, a salt of a Group IA or Group IIA metal which does not causeprecipitation of a copper or palladium salt, can be employed.

The heterogeneous catalysts can be employed in oxidation reactions, andparticularly for converting CO to CO and S0 to S0 at temperatures of theapproximate range of from about 0 to about 300 C., and preferably fromambient temperature to about 150 C.

Total pressure can be atmospheric, suband superatmospheric, with thoseapproximating atmospheric being preferred.

With regard to gas flow rates, a minimum of about 0.1 second contacttime is employed. An upper limit is governed by considerations ofpractical economics (and upon how rich the gas stream is in oxidizablecontaminant gases). Preferred contact times range from 0.3 to 3.0seconds.

With employment of the heterogeneous catalysts, it is recommended thatmolecular oxygen also be included in TABLE I CuClz, C11(NO3)2, Percentpercent percent conversion Total of total of total of CO to Cu saltPdClz LiCl Cu salt Cu salt C02 1.00 M .0020 M 100 Nil I Nil 1.00 M .0020M 80 20 3 Nil 100 M .0020 M 60 0.4 1 00 M .0020 M 40 4. 2 1.00 M- .0020M 20 8O 58 1.00 VI 0020 M Nil 100 I Nil 0.97 0080 M 100 Nil 26 0.97 0080M 20 41 0.97 0080 M 60 40 72 0.07 0080 M 40 60 b 0.97 0080 M 20 80 780.97 0080 M Nil 0.8

B No detectable CO2; threshold of detection is 0.2% conversion level.

b A white precipitate of cuprous hydroxide u as formed after 10 minutesoperation.

0 A white precipitate of cuprous hydroxide and a dark precipitate of Pdand/or PdO was formed after 10 minutes operation.

Example 2 The apparatus and procedure of Example 1 was employed. Gasflow rate was regulated at 630:10 ml. of CO per minute. All runs wereconducted at 23 C. LiCl concentration in each run was approximatelytwice the concentration of the palladium or rhodium chlorideconcentration.

PdCl was compared with Rhcl Various combinations of cupric salts wereused. Comparison is also given of ferric salts and of organic redoxcompounds, in pla of the cupric salts.

Results are provided in Table II.

TABLE II Gas- Percent liquid conversion contact of O0 to Pd or Rh Cupricsalts, etc. time, sec. 002

Nil CD012, 0.50 M, Ou(NO3)2, 0.50 M 1. 5 8 Nil PdClz, .005 M CuClz, 0.50M, CuSO4, 0.50 M 1. 6 31 PdOlz, .005 M CuBrz, 0.50 M, C11(NO3)2, 0.50M 1. 9 32 RhCla, .005 M CUC1z,O.5O M, C11(N03)2, 0.50 M 1.3 Nil PdClz,.005 M FeCla, 0.50 M, Fe(NOs)3, 0.50 M 2.5 :0. 4 PdClz, .005 M.-.p-Benzoquiuone, 2.0 M in 1,2 propanediol :0. 4 PdClz, .0025 1p-Benzoquinone, 1.0 Min a 1:1 mixture (vol/vol.) of ethanol and 2. 15

1,2-propanediol. PdClz, .005 M 011012, 0.50 M, Cu(NO3)2, 0.50 M (freshmixed with Pd salt) 1. 3 l7 PdCh, .005 M CuClg, 0.50 M, C11(NO3)2, 0.50M (after three hours standing) 1. 3 82 e No detectable CO2; threshold ofdetection is 20.2%.

the reaction system. In order to have catalyst life-times of practicalduration, molecular oxygen is present in at least stoichiometricquantities in the gas stream being treated.

ILLUSTRATIVE EXAMPLES The homogeneous solutions and oxidation reactionstherewith, are illustrated by the following examples.

Example 1 To a 500-m. gas-scrubbing bottle fitted with a standard coarseglass diffusing frit was added 100 ml. of an aqueous solution. A mixtureof helium 98% and carbon monoxide 2.00% was then passed through thediifusing frit at atmospheric pressure and at 23 C. The gas flow ratewas 640-340 ml./min. and the mean-gas-liquid contact time (based uponsolution and overhead foam volumes) was 1.9:01 sec. Samples of exit gaswere collected at 9.0 minutes and again at 10.0 minutes after the gasflow was started; these were analyzed by quantitative gas chromatographyfor carbon monoxide and for carbon dioxide. The results, expressed forvarious aqueous solutions as percent conversion of CO to CO are shown inTable I below and in the drawing.

The aqueous solutions were prepared by dissolving PdCl LiCl, CuCl andCu(NO in water at about 20- 25 C.

Example 3 A series of runs was. carried out in which 1.5 liters of anaqueous solution was mixed vigorously with sulfur dioxide gas at 1.0atm. pressure, for 20 minutes at 24 C. Mixing was accomplished bychurning with a gasliquid mixing device in a 3.0-liter glass flask,adding make-up sulfur dioxide to the gas phase continuously so as tomaintain pressure. The solution was then degassed by agitation underreduced pressure for five minutes, purged with air, refluxed for 30minutes, cooled, and aliquots withdrawn and titrated with standard baseto determine acid normality.

Under this regimen the dissolved S0 is very substantially removed, sothat in the case of no oxidation (see Run #1), the acid concentration inthe degassed solution is very low. To the extent that oxidation of S0has occurred, however, sulfuric acid will have been formed, and thisacid cannot be removed from aqueous solutions by any degassingtechnique. The extent of formation of sulfuric acid, as measured by thedevelopment of the permanent acidity, measures the extent of oxidationof sulfur dioxide.

Run #1. This run was carried out with 1.5 liters of water. The water wascompletely saturated with sulfur dioxide within 15 minutes. Afterdegassing, titration of 7 aliquots with a standard base showed theresidual acidity (due to sulfurous acid) to be 0.015 N ($0.001).

Run #2. This run was carried out as Run #1, except that the water wasreplaced with 1.5 liters of an aqueous solution containing 0.50M cupricchloride and 0.50M cupric sulfate. After treatment as in Run #1, thegross titratable acidity was found to be 2.006 N ($0.006). Aftercorrecting for the effective acidity of the cupric salts, the net gainin acidity upon 20 minutes contact with S was 0.39 N.

Run #3. This was carried out in the same manner as Runs #1 and #2,except that the 1.5 liters of aqueous solution contained 3.55 Mpalladous chloride, 0.50M cupric chloride, and 0.50M cupric sulfate. Thegross titratable acidity was found to be 2.641 N (r0013), which aftercorrecting for the effective acidity of the salts showed a net gain of0.96 N. This amount of formed acid is approximately 2 fold greater thanthat in Run #2 and approximately sixty-fold greater than that in Run #1.

Example 4 A stream of helium containing 2 10 p.p.m. CO was passedthrough an aqueous solution containing 0.020 M PdCl 1.00 M CuCI and 1.00M Cu,NO In each of three standard gas-washing bottles (250 ml. capacity,fitted with coarse fritted glass diffusers) was placed 150 ml. ofcatalyst solution, and the three bottles were connected in seriesdownstream of a flowmeter connected to a cylinder containing thehelium-carbon monoxide mixture. The cylinder valve was set to permit aflow of 235 ml./ min. through the system. After min. of operation at 22C., a portion of untreated feed gas was then collected for comparison.

The gas samples were analyzed by gas chromotograph, with a standardthermal conductivity instrument (Aerograph Model 2021C) fitted with a 6ft. x A in. column of Porapak Q for carbon dioxide assay and a 6 ft. x Acolumn of molecular sieve 5A for carbon monoxide assay, bothdeterminations run at a column temperature of C. Assays were made inquadruplicate, with retention of the best three of each set of fourdeterminations.

Data is given below in Table III, showing that the CO content of the gasmixture is reduced from 2.0 to 0.06%, at the same time that a major COpeak appears, as a result of passage through the catalyst system. Crossanalysis of the untreated gas shows the presence of a small amount of COabout 0.05 as an initial impurity.

This study, with an effective gas-liquid contact time of about 1.5 sec.,shows that a gas stream containing 2x10 p.p.m. carbon monoxide can betreated to effect conversion of 97% of the CO to CO TABLE III Gaschromatographic analyses of gas mixture 1 CO, percent CO2, percent Feedgas 2.02 (Avg. 2.00%)-...{ 0.031 }(Avg. 0.05%).

2. 02 0. 04s 0. 05s 2. 03 Efliuent gas 0.07] (Avg. 0.06% 2.00 (Avg.2.00%).

Nora-SD of analyses: Overall==0.02l% as CO (8 DF), low ranged: 0.010% asCO (4 DE).

Heterogeneous catalysts and oxidation reactions therewith, areillustrated by the following examples.

Example 5 Four solid catalyst systems were prepared by contactingportions of an aqueous catalyst solution with each of the following: (a)Molecular Sieve 5A, a crystalline aluminosilicate marketed by UnionCarbide; (b) silica gel; (0) activated alumina, and (d) activatedcharcoal 'Norit A marketed by Matheson Coleman & Bell. The catalystsolution comprised: PdCl 0.01 M; LiCl, 0.02 M; CuCl 0.788 M; Cu(NO 0.98M, and the balance water.

To 50-ml. portions of the above catalyst preparation solution were added10.0-g. portions of each of several solid catalyst supports, describedin Table IV below. The mixtures were slurried for 15 minutes at roomtemperature, then the solids were collected by suction filtration anddried for five minutes by an aspirator air stream. Then, the resultingmoist cakes were broken up and the solids dried overnight at 20 mm.pressure. The solids were then further dried at 60 C. and 20 mm.pressure for an additional 24 hours. Each supported catalyst powder wasthen weighed to determine the amount of catalyst picked up, then packedinto a copper column 36 inches long and 0.190 inch internal diameter,closed with loose glass-wool plugs to prevent catalyst loss.

The pickup of weight for each of four catalyst supports, and theindicated concentrations of components per kilogram of catalyst support,is:

The average weight increase of each support is 19%. It appears that theconcentration of palladium (II) in each of the four catalysts is about0.003-0.01 moles/ kg. support.

In the experiments, a stream of helium containing 2.00% carbon monoxide(CO) and a stream of compressed air were combined in an atmosphericpressure manifold, and the resulting mixed stream was passed through astandard 500 ml. gas sparger containing 150 ml. of water, thushumidifying the gas mixture. The gas mixture was then passed through asection of copper tubing (36 inches by 0.250 inch outside diameter,0.190 inch inside diameter, and with approximately 24 inches of thelength packed with the solid catalyst-and-support combination beingtested), and then to an exit vent from which samples were periodicallywithdrawn. For a control run with no supported catalyst, the exit samplewas withdrawn immediately downstream of the humidifying gas sparger.Crude flow controls of the air and the helium- CO streams wereaccomplished by floating ball flowmeters; however, the actual amount ofair in the gas mixture was determined more accurately in the course ofgas chromatographic analysis of the exit gas samples.

Gas chromatographic analysis was obtained on samples collected instandard ml. gas collection flasks which were evacuated immediatelyprior to sampling. Analysis was carried out with 2.00 ml. gas samplesusing a parallelcolumn assembly (Porapak Q packing in one leg, 10 ft. xinch, and Molecular Sieve in the other leg, 4 ft. x A inch) at C.injector 165 C., detector (thermal conductivity, at milliamperes) 240C., and a helium fiow rate of 50 ml./min.

The results of these runs are shown in Table IV. Except for the controlrun, which showed no detectable conversion, eight runs with four solidsupports show CO conversions of from 2% to 100%.

TABLE IV Gas- Time on Percent catalyst Percent eonstream, air in contactverston of CO Catalyst support min. feet gas a time b to 002 Molecularsieve A, 80/100 mesh 20 15 1. 7 60 (61, 59) Do 47 3 2.0 53 (52, 53)Silica gel, Grade 12, 28/200 mesh 15 8 1. 7 2 (2. 2, 2) Do 37 7 1. s 44(43, 44 Do- 51 4 2.0 51 (50, 51) Alumina, chromatographic gr de, 80/325mesh 20 29 100 95 (94, 95) Do. 4O 23 115 d 100 (100,100) Charcoal, NoritA, fine powder 47 64 100 d 100 (100,100) Control (no catalyst) 13 6 Nilu Determined by quantitative gas chromatography of the exit gas h Basedupon the estimate that 70% of tubing internal volume is filled bycatalyst and solid support: contact time=o30 (nominal tube volume)(flowmeter flow rate).

Q Determined by quantitative gas chromatography; figures in parenthesesare replicate individual determinations.

d No detectable residual 00; threshold of detection is about 0.2% of thefeed concentration. a No detectable 00:; threshold of detection is about0.3% of the feed concentration of CO for these experiments.

What is claimed is:

1. An aqueous homogeneous solution consisting essentially of (a) aWater-soluble palladium (II) salt, said salt being selected from thegroup consisting of a chloride, bromide, nitrate, sulfate, and Li PdClhaving a concentration of metal ion of at least about 0.00005 to about0.025 mole per liter, (b) a copper (II) chloride or bromide, (c) acopper (II) salt selected from the group consisting of a nitrate,sulfate, alkylsulfonate, arylsulfonate, tetrafluoroborate, perchlorate,trifluoroacetate, trichloroacetate and methanephosphonate, and (d) thebalance water, wherein the total concentration of (b) and (c) is fromabout 0.003 to about 3 moles per liter, and wherein the copper (II)chloride or bromide (b) comprises from about to about 80 mole percent ofthe total of (b) and (c).

2. A solution of Claim 1 wherein the palladium salt (a) is palladium(II) chloride.

3. A solution of Claim 1 wherein the concentration of (a) is from about0.001 to about 0.02 mole per liter.

4. A solution of Claim 1 wherein the copper (II) halide (b) is copper(II) chloride.

5. A solution of Claim 1 wherein the copper (II) salt (c) is copper (II)nitrate.

6. A solution of Claim 1 wherein the copper (II) halide (b) comprisesfrom about 15 to about 60 mole percent of the total of (b) and (c).

7. A solution of Claim 1 wherein the palladium (II) salt is Li PdCl 8. Asolution of Claim 7 wherein said solution is aged. 9. A compositionconsisting essentially of (a) from about 0.0003 to about 0.03 gram-molesof a water-soluble palladium (II) salt selected from the groupconsisting of a chloride, bromide, nitrate, sulfate and Li PdCl (b) fromabout 0.001 to about 1.5 gram-moles of cop per (II) salts, wherein acupric (II) chloride or bromide comprises from about 10 to about molepercent of the total of (b) and the balance is a copper (II) saltselected from the group consisting of a nitrate, sulfate,alkylsulfonate, arylsulfonate, tetrafluoroborate, perchlorate,trifluoroacetate, trichloroacetate and methanephosphonate.

10. A composition of Claim 9 deposited upon a carrier.

References Cited UNITED STATES PATENTS 3,102,919 9/1963 Hirschbeck etal. 252441 X 3,154,586 10/1964 Bander et al 252438 X 3,410,807 11/1196 8Lloyd 252429 R 3,790,662 2/1974 Lloyd et al. 252441 X PATRICK P. GARVIN,Primary Examiner US. Cl. X.R.

1. AN AQUEOUS HOMOGENEOUS SOLUTION CONSISTING ESSENTIALLY OF (A) AWATER-SOLULBE PALLADIUM (II) SALT, SAID SALT BEING SELECTED FROM THEGROUP CONSISTING OF A CHLORIDE, BROMIDDE, NITRATE, SULFATE, ANDLI2PDCL4, HAVING A CONCENTRATION OF METAL ION OF AT LEAST ABOUT 0.00005TO ABOUT 0.025 MOLE PER LITER, (B) COPPER (ii) CHLORIDE OR BROMIDE, (C)A COPPER (II) SALT SELECTED FROM THE GROUP CONSISTING OF A NITRATE,SULFATE, ALKYLSULFONATE, ARYLSUFONATE, TETRAFLUOROBORATE, PERCHLORATE,TRIFLUOROACETATE, TRICHLOROACETATE AND METHANEPHOSPHONATE, AND (D) THEBALANCE WATER, WHEREIN THE TOTAL CONCENTRATION OF (B) AND (C) IS FROMABOUT 0.003 TO ABOUT 3 MOLES PER LITER, AND WHEREIN THE COPPER (II)CHLORIDE OR BROMIDE (B) COMPRISES FROM ABOUT 10 TO ABOUT 80 MOLE PERCENTOF THE TOTAL OF (B) AND (C).